An autopsy result has shown no evidence of foul play in the death of Enron founder Kenneth Lay, involved in the biggest corporate scandal in the United States.

Lay, 64, died on Wednesday, while holidaying near Aspen, Colorado, six weeks after being found guilty of fraud and conspiracy.

"There was no evidence of foul play," said Dr Robert Kurtzman, the forensic pathologist who performed the post-mortem examination.

"The cause of death is coronary artery disease," he said, adding that the examination showed that Lay had previously suffered a heart attack.

Still pending are the results of a toxicology report and microscopic analysis of his tissues, Kurtzman, Mesa County coroner, told reporters in Grand Junction, where Lay's body had been transferred.

The former chief executive who had been awaiting sentencing, faced decades in prison in connection with Enron's 2001 bankruptcy, died before he could ever serve time in prison.

On Friday, federal prosecutors asked a federal judge to force Lay to forfeit $43.5 million they said he had received because of his crimes at Enron.

But when a defendant who pleaded not guilty dies before sentencing, as Lay did, in most cases the conviction is wiped out on the grounds that the defendant did not have the opportunity to appeal, legal experts said.